Method of delivering frac fluid and additives

ABSTRACT

A method for the controlled delivery of a fracturing fluid to a well bore comprises formulating an aqueous base fluid such that it meets or exhibits desired physical and chemical characteristics for an optimal fracturing fluid. The formulation of the aqueous base fluid max involve commingling one or more sources of waste water with a source of fresh water followed by controlled injection of one or more additives. This process is substantially completed prior to delivering the aqueous base fluid to the well site. This allows the delivery of an optimal volume of the aqueous base fluid with homogeneously blended additives to the well bore.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 15/675,950,filed Aug. 14, 2017 (issuing as U.S. Pat. No. 10,082,011 on Sep. 25,2018), which is a continuation of U.S. patent application Ser. No.14/847,925, filed Sep. 8, 2015 (issued as U.S. Pat. No. 9,732,602 onAug. 15, 2017), which is a continuation of U.S. patent application Ser.No. 14/034,699, filed Sep. 24, 2013 (issued as U.S. Pat. No. 9,127,537on Sep. 8, 2015), which is a continuation of U.S. patent applicationSer. No. 13/685,940, filed Nov. 27, 2012 (issued as U.S. Pat. No.8,540,022 on Sep. 24, 2013), which was a continuation of U.S. patentapplication Ser. No. 13/453,210, filed Apr. 23, 2012 (issued as U.S.Pat. No. 8,316,935 on Nov. 27, 2012), which was a continuation of U.S.patent application Ser. No. 12/555,401, filed Sep. 8, 2009 (issued asU.S. Pat. No. 8,162,048 on Apr. 24, 2012), which claims benefit of U.S.Provisional Patent Application Ser. No. 61/191,528 filed Sep. 9, 2008.Each of these applications are incorporated herein by reference, andpriority to/of each of which is hereby claimed.

BACKGROUND OF THE INVENTION

Fracturing is the process of creating fractures in oil and gasformations to stimulate or increase production in oil and gas wells. Thefrac or fracturing operation involves the injection of fracturing fluidinto the wellbore at sufficient pressures, flow rates and volumes tofracture the surrounding formation. The fracturing fluid may comprise abase fluid, such as water or gels, and a variety of additives includingpolymers, friction reducers, cross-linkers, anti-scaling agents,proppants and biocides. The fracturing forms a conductive flow path forhydrocarbons. However, once the fluid pressure in the fracture drops,the fracture closes. Therefore, proppants are injected with the basefluid to fill the fracture and prop it open. Materials used forproppants may include sand, ceramics and glass beads.

SUMMARY OF THE PRESENT INVENTION

The one or more embodiments of the invention facilitate the delivery ofoptimal volumes of a fracturing fluid containing optimal concentrationsof one or more additives to a well bore. Conventional practice involvespre-staging large volumes of fracturing fluid with ad hoc additions ofone or more additives. This results in poor or non-homogeneousdispersion of the additives, and frequently results in wasteful,non-optimal additive concentrations. In contrast, the one or moreembodiments of the invention allow for accurately and preciselycontrolling the volume of the fracturing fluid delivered, at high flowrates, to the well bore. Advantageously, the fracturing fluid may alsocontain accurately and precisely controlled concentrations of one ormore additives. In one or more embodiments, the concentration of theadditives may be extremely small, even trace amounts, when compared tothe large volume of the aqueous base fluid in which the additives aredispersed. One or embodiments of the invention disclose repeated testingand analysis of an aqueous base fluid which is utilized in formulatingthe fracturing fluid, in-line and prior to delivery to the well site. Asa consequence of this testing and analysis, accurate adjustments to thephysical and chemical characteristics of even large volumes, typicallyhundreds of thousands of gallons, of the aqueous base fluid may be madethrough the introduction of precise concentrations one or moreadditives. Since the additives may be blended in-line in the aqueousbase fluid, prior to its delivery to the well site, the additives arehomogeneously dispersed in the aqueous base fluid by the time theaqueous base fluid is used to formulate the fracturing fluid. In oneembodiment of the invention, only optimal volumes of the aqueous basefluid are delivered to the well site. The testing and analysis continuesat the well site, and also during the pumping of the aqueous basefracturing fluid into the well bore. Adjustments to the additiveconcentration may also be made to large but optimal volumes of thefracturing fluid pumped at high flow rates, from 5 to 150 bbls/minute,such that only optimal concentrations of the additives are utilized inthe fracturing operation.

In one embodiment of the invention, a method for the controlled deliveryof a fracturing fluid to a well bore comprises determining one or moreavailable sources of an aqueous base fluid for the fracturing fluid. Theone or more available sources of the aqueous base fluid comprises lakes,rivers, ponds, creeks, streams, well water, fluid effluent fromindustrial processes, brines, processed fluids, flowback fluids, pitwater, spudder water, and other waste waters or fluids. One or moresamples of each source may be individually tested to determine itsphysical and chemical characteristics, followed by comparing thephysical and chemical characteristic data of each available source withpredetermined physical and chemical characteristic data for an optimalfracturing fluid to identify suitability of the fluid source for afracturing operation. A source of aqueous base fluid that comparesfavorably to the optimal fracturing fluid may be selected for deliveryto the fracturing operation at the well site. The aqueous base fluid maybe transported to one or more fracturing fluid tanks. The aqueous basemay be transported by trucking or using a pumping mechanism with one ormore pipelines connecting the pumps to the fracturing fluid tanks. Inanother embodiment, the one or more fracturing fluid tanks are groupedinto one or more sets, wherein each set contains one or more fracturingfluid tanks. One set of fracturing fluid tanks may be positionedproximate a source of the aqueous base fluid for conveniently deliveringthe aqueous base fluid to a second set of fracturing fluid tanks thatmay be located proximate a well site. In another embodiment of theinvention, the aqueous base fluid may be pumped from the source to afirst set of fracturing fluid tanks, and thereafter pumped to a secondset of fracturing fluid tanks.

One or more samples of the aqueous base fluid may be tested in thefracturing fluid tanks to determine its physical and chemicalcharacteristics. The physical and chemical characteristics may compriseflow rate, pH, viscosity, ionic strength, volume, homogeneity, specificchemical concentrations, density, crystallization temperature, biocidedemand and combinations thereof. Measurement of the physical andchemical characteristics is made using flow meters, pH meters,conductivity meters, and other instruments known in the art. Thesephysical and chemical characteristic data may be then compared to thepredetermined physical and chemical characteristic data for the optimalfracturing fluid.

In the event of a failed comparison, that is, if the physical andchemical characteristics of the sampled fluid differs from those of theoptimal fracturing fluid, one or more additives, may be continuouslyintroduced into the aqueous base fluid until it achieves thepredetermined physical and chemical characteristics. Thus, for instance,if the aqueous base fluid is found to have scaling properties,anti-scaling additives may be introduce to the aqueous base fluid. Onthe other hand, if the aqueous base fluid is found to be corrosive,anti-corrosive chemicals may be introduced to the aqueous base fluid.The additives may be selected from a group comprising biocides, pHmodifiers, corrosion inhibitors, friction reducers, scale inhibitors,oxygen scavengers, hydrogen sulfide, oxidizing agents, viscosifiers andcombinations thereof. In one embodiment of the invention, the biocidecomprises an oxidizing biocide. In another embodiment, the oxidizingbiocide comprises a bromine biocide. The additives may be blended intothe aqueous base fluid until they are homogeneously dispersed. Theaqueous base fluid blend may be delivered to the well site for thefracturing operation. At the well site, the aqueous base fluid blend isused to formulate the fracturing fluid. Formulation of the fracturingfluid involves introduction of additives and/or one or more proppants tothe aqueous base fluid blend. An optimal volume of the fracturing fluidis pumped at high flow rates to the well bore for fracturing thesurrounding formations. The optimal volume of the fracturing fluidfurther comprises an optimal concentration of the homogeneouslydispersed additives. In one embodiment of the invention, the optimalvolume of the fracturing fluid is pumped to the well bore at from 5 to150 bbls/minute. In another embodiment of the invention, the optimalvolume of the fracturing fluid is pumped to the well bore at from 15 to120 bbls/minute. In yet another embodiment of the invention, the optimalvolume of the fracturing fluid is pumped to the well bore at from 60 to100 bbls/minute.

In another embodiment of the invention, the aqueous base fluid from twoor more of the sources may be commingled in the event the individualsources are unsuitable for the fracturing operation. At least one of thecommingled sources may comprise water or fluids from another source,such as, spudder water, pit water, flowback fluid or other waste fluidsgenerated during oil and gas production operations. These fluids have tobe disposed and the disposal of the fluids entails transportation costs.By recycling these fluids (by commingling it with another source,typically a source of fresh water) as a base fluid for the fracturingoperation, the well operator may save disposal costs, and have a readilyavailable supply of the aqueous base fluid. It may also be possible tocut down on the huge volumes, typically tens of thousands of barrels, ofthe fresh water or frac water that is required for fracturing the wells,since the fresh water is now commingled with the easily available wastefluids.

The commingled aqueous base fluid may be transported to the fracturingoperation in a first set of fracturing fluid tanks in the event thecommingled aqueous base fluid is identified as suitable for thefracturing operation. One or more samples of the commingled aqueous basefluid may be tested in the first set of fracturing fluid tanks todetermine its physical and chemical characteristics. In anotherembodiment of the invention, one or more samples of the commingledaqueous base fluid may be tested in-line while it is pumped to a firstset of fracturing fluid tanks.

The physical and chemical characteristic data of the commingled aqueousbase fluid may be compared to the predetermined physical and chemicalcharacteristic data for the optimal fracturing fluid. If thecharacteristics are comparable, the commingled aqueous base fluid may betransported to the well site. If the physical and chemicalcharacteristics of the commingled aqueous base fluid are not comparableto the optimal fracturing fluid, one or more additives may becontinuously introduced into the commingled aqueous base fluid toachieve the same characteristics. The one or more additives may beblended into the commingled aqueous base fluid until it is homogeneouslydispersed.

In one embodiment of the invention, the additives may be introduced in acontrolled manner by one or more metering pumps. The addition ofadditives may be conducted in real-time. The metering pumps may bemonitored at a control center manually or automatically. The controlcenter may comprise one or more computers comprising a computer programproduct for automatically adjusting the dosage rates of the additives.The dosage rate may depend on a formation to be fractured, theconditions of a specific well and the physical and chemicalcharacteristics of the commingled aqueous base fluid. The adjustments tothe dosage rates may be made on-the-fly. The adjustments to the dosagerates may be made as-needed. The monitoring of metering pumps andadjustments to the additive dosage rate may also be conducted inreal-time.

In one embodiment of the invention, a bromine-based biocide may be addedto the commingled aqueous base fluid if it is determined to containbacterial or other microbial living organisms. The bromine biocide ishomogeneously dispersed within the commingled aqueous base fluid. Thebromine biocide may be added in-line during pumping to the second set offracturing fluid tanks or at the second set of fracturing fluid tanks,but prior to transportation to the well site. This ensures adequatebacterial/microbial “kill time” for the biocide to effectively eliminatethese organisms. The addition of the bromine biocide may be automated.

The commingled aqueous base fluid blend may be delivered to a second setof fracturing fluid tanks when the commingled aqueous base fluid blendachieves the predetermined physical and chemical characteristics. One ormore samples of the commingled aqueous base fluid blend may becollected, monitored and tested in-line during delivery to the secondset of fracturing fluid tanks. The physical and chemical characteristicsof the commingled aqueous base fluid blend may be continuously adjustedby introducing additives in-line and/or at the second set of fracturingfluid tanks. The second set of fracturing fluid tanks containing thecommingled aqueous base fluid blend may be transported to the well sitewhen the commingled aqueous base fluid blend achieves the predeterminedphysical and chemical characteristics.

In one embodiment of the invention, the second set of fracturing fluidtanks may be located at a distance from the well site. The commingledaqueous base fluid blend may be transported from the second set offracturing fluid tanks to a third set of fracturing fluid tanks locatedat the well site when the commingled aqueous base fluid blend achievesthe predetermined physical and chemical characteristics.

One or more samples of the commingled aqueous base fluid blend may betested at the well site to determine its physical and chemicalcharacteristics. The testing at the well site may be carried out inreal-time using one or more simplified field test kits. Based on thetesting results, one or more additives, such as viscosifiers, and/or oneor more proppants may be added to, or their concentrations adjusted in,an optimal volume of the commingled aqueous base fluid blend to achievethe predetermined physical and chemical characteristics. The additivesand/or proppants may be blended in the commingled aqueous base fluid toform the fracturing fluid. The one or more proppants further comprisesand particles, resin-coated particles, mineral fibers, ceramicparticles, glass beads, aluminum pellets and mixtures thereof. Thecommingled aqueous base fluid blend may be pumped to a hopper or mixingequipment for admixing with the additives and/or proppants.

Conventional or existing practice involves introduction of one or moreadditives to the formation independent of the fracturing operation. Theadditives are added at the production site either directly into the wellbore or by mixing in a hopper or mixing equipment along with largevolumes of the fracturing fluid, proppants and other substances neededin the fracturing operation. This results in inadequate dispersion ofthe additives in the fracturing fluid and the blend is not homogeneous.The process also does not allow for the monitoring and feedback neededto control the rate of addition of the additives to the fracturingfluids. The well operators, therefore, do not have control over theadditive concentration delivered to the formation, or whether aneffective amount of additives has been added, or whether too muchadditives have been added in the fracturing operation. This results ininadequate or excessive concentrations of additives being used in thefrac or fracturing operation. This adversely impacts the fracturingoperation, resulting in loss of production. Furthermore, large volumesof one or more fracturing fluids are required in the fracturingoperation since adequate information on the composition, flow ratesand/or interaction between the one or more fracturing fluids and the oneor more additives is not easily available. The well operators typicallyemploy larger than necessary fracturing volumes in an attempt toovercome this lack of information. All of this results in an inefficientand costly process. There is also an environmental cost associated tothis, since the flowback fluids return from the well bore after thefracturing operation is completed and have to be cleaned up, and properdisposal of certain toxic additives comprising biocides and surfactantshas to be ensured, at the end of the fracturing process. Embodiments ofthe invention teach an efficient and cost-effective method for thecontrolled delivery of fracturing fluids to the well bore.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the Langelier Saturation Index (“LSI”) values of a firstset of individual test fluids.

FIG. 2 shows an embodiment of the invention.

FIG. 3 shows the LSI values of a first blended or commingled fluid.

FIG. 4 shows the LSI values of a second set of individual test fluids.

FIG. 5 shows another embodiment of the invention.

FIG. 6 shows the LSI values of a second set of blended or commingledfluids.

DETAILED DESCRIPTION

Embodiments of the invention disclose a method for delivering an aqueousbase fluid with desired physical and chemical characteristics to a wellsite or rig site for the preparation of a fracturing fluid at the wellsite. The desired physical and chemical characteristics may be achievedthrough blending aqueous base fluids from multiple sources, includingpossibly waste water sources, and/or through the controlled introductionof any required additives to an individual source of the aqueous basefluid. The method of this invention allows for better monitoring of theintroduced additives while controlling the volume of the fracturingfluids. In yet another embodiment, since the additives are introduced toand blended with the aqueous base fluid prior to reaching the well site,the additives are homogeneously dispersed within the aqueous base fluid.The homogenous dispersion of additives in the aqueous base fluidoptimizes the efficacy of the fracturing fluid containing the aqueousbase fluid in fracturing operations. Embodiments of the invention mayaccelerate production and increase the economic viability of wells andthus, reduce the pressure to abandon wells prematurely.

In one embodiment of the invention, aqueous base fluid from one or moreavailable sources is collected. The aqueous base fluid may be obtainedfrom one or more available sources comprising fresh water, processedfluids, brines, and other waste water. Fresh water sources furthercomprise lakes, rivers, ponds, creeks, streams and well water. Theprocessed fluids further comprise spudder water, recycled flowback fluidfrom wellbores and fluid effluents from wells or industrial processes.

The composition and the physical, chemical and biological properties ofthe aqueous base fluid may differ depending on their source. One or moresamples of the aqueous base fluid is collected from each source andtested to determine its relevant physical and chemical characteristicdata. The physical and chemical properties to be determined may comprisefluid flow rate, pH, volume, homogeneity, viscosity, specific chemicalconcentrations, density, crystallization temperature, and combinationsthereof. The aqueous base fluid may also be tested for compatibilitywith selected additives and cost effectiveness and ease of removal fromthe formation, ibis data is compared against predetermined physical andchemical characteristic data for a preferred or an optimal aqueous basefracturing fluid suitable for a particular fracturing operation. If thecomparison is favorable, the aqueous base fluid from a given source maybe selected for delivery to the well site.

In one embodiment, the aqueous base fluid from a selected source may bepumped or trucked to one or more fracturing fluid tanks. In anotherembodiment of the invention, aqueous base fluid from multiple sourcescan be blended or mixed to form a commingled aqueous base fluid.Advantageously, spudder water, flowback fluids or other waste waters orfluids generated during the drilling and production operations may beblended with fresh water to create the aqueous base fluid. Thisrecycling of waste waters may also be desirable due to expensivedisposal costs, both economic and environmental. Additionally, sincelarge volumes of fracturing fluids are required to fracture theformation, procuring and transporting such large volumes of aqueous basefluids that meet specification or comply with predetermined physical andchemical characteristics may not always be easily possible. Comminglingallows the use of waste fluids, for example, along with lesserquantities of fluids, such as fresh water. The commingled fluid iscloser in physical and chemical characteristics to an optimal fracturingfluid. In one or more embodiments, the commingled aqueous base fluidrequires less to no additives to achieve the predetermined physical andchemical characteristics when compared to using an aqueous base fluidfrom waste water sources, for example. Although hereinafter the specificembodiments are described with reference to the commingled aqueous basefluid, it should be understood that in other embodiments, individualsources of aqueous base fluid that meet the predetermined physical andchemical characteristics may be used in lieu of the commingled aqueousbase fluid. Such individual sources of aqueous base fluid are intendedto be encompassed within the scope of this invention.

The density of the commingled aqueous base fluid may range from 8.33 to19.5 lb/gal. The fracturing fluid tanks may be grouped into one or moresets, wherein each set contains one or more fracturing fluid tanks. Inone embodiment, a first set of fracturing fluid tanks is locatedoff-site from the production facility. In another embodiment, the firstset of fracturing fluid tanks is conveniently located at the well site.

The commingled aqueous base fluid in the first set of fracturing fluidtanks may be tested to determine its physical and chemicalcharacteristics. One or more samples of the commingled aqueous basefluid are collected at one or more sampling stations or sampling portsat the first set of fracturing fluid tanks. In one embodiment, thecommingled aqueous base fluid samples are obtained from each fracturingfluid tank.

The commingled aqueous base fluid samples may be tested for variouscharacteristics comprising fluid composition, viscosity, and otherphysical and chemical properties. Each fracturing operation requiresfracturing fluids of varying volumes, flow rates, physical and chemicalproperties. The test results from the first set of fracturing fluidtanks are compiled and analyzed to determine the commingled aqueous basefluid suitability for one or more fracturing operations. The results canalso be stored using a computer program product for ready accessibilityin the future.

In another embodiment, the commingled aqueous base fluid that meets therequirements of a particular fracturing operation is pumped to a secondset of fracturing fluid tanks. Pipelines may be set up to accommodateone or more pumps. The second set of fracturing fluid tanks may belocated offsite or proximate the well site. Samples of the commingledaqueous base fluid may be collected inline during the pumping to thesecond set of fracturing fluid tanks. The samples are again tested forkey physical and chemical characteristic data. In the event of a failedcomparison, one or more additives may be continuously introduced intothe commingled aqueous base fluid in order for it to achieve the desiredor predetermined physical and chemical characteristics. In oneembodiment, the additives are directly injected in the commingledaqueous base fluid at one or more injection points along the pipeline.

The additives may perform several beneficial functions such as pHmodification, killing microbial agents and corrosion inhibition. Theadditives may be selected from a group comprising biocides, pHmodifiers, corrosion inhibitors, emulsion breakers, anti foams, hydrogensulphide and oxygen scavengers, surface tension reducers, shale and claystabilizers, paraffin/asphaltene inhibitors, scale inhibitors, andcombinations thereof. In one embodiment of the invention, the additivecomprises an oxidizing biocide. In another embodiment, the biocidecomprises an organic and biodegradable bromine-based biocide.

The test samples may be repeatedly collected and analyzed and additivesadjusted so that the addition of one additive does not createincompatibilities with the commingled aqueous base fluid and/or otheradditives. Sampling and testing may be repeated after each additive isadded to the commingled aqueous base fluid until an optimal combinationof additives is reached and the commingled aqueous base fluid achievesthe desired or predetermined physical and chemical characteristics. Inanother embodiment, the sampling, testing and adjustment steps may berepeated at the second set of fracturing fluid tanks. In one embodiment,this testing and adjustment process is carried out manually and inreal-time. In another embodiment, this testing and adjustment process isautomated.

The additives may be introduced into the commingled aqueous base fluidby means of one or more metering pump. The metering pumps are observedor monitored in real-time by a control center. In one embodiment, thecontrol center comprises one or more computers. The computers furthercomprise a computer program for adjusting the dosage rates of theadditives depending on the formation to be fractured, the conditions ofthe specific well and the physical and chemical characteristics of thecommingled aqueous base fluid. The additives are mixed inline or at thepumps with the commingled aqueous base fluids to ensure homogeneousdispersion and blending. One or more samples of the commingled aqueousbase fluid blend are collected from sampling ports at the pumps or alongthe pipeline. The samples are tested for physical and chemicalcharacteristics, and additional additives are introduced or dosage ofthe additives is adjusted if required.

In one embodiment, the testing of the commingled aqueous base fluidblend taken from a sample port is performed at the sample port itselfand the resulting data is also analyzed at the sample port. The analyzeddata is sent to one or more computers at a control center to determineinformation necessary to adjust additive dosage to achieve thepredetermined physical and chemical properties for the commingledaqueous base fluid blend. This information is looped to the meteringpump which injects the required volume, concentration and/or combinationof one or more additives.

In another embodiment, the commingled aqueous base fluid blend takenfrom a sample port is tested at the control center and the result isprocessed and analyzed by the one or more computers at the controlcenter. The instructions for making necessary adjustments, as analyzedby the one or more computers, are sent to the one or more metering pumpsto adjust or control the amount of additive to be introduced to thecommingled aqueous base fluid blend. In yet another embodiment, theinstructions for making the necessary adjustments, as analyzed by theone or more computers, are sent to the one or more metering pumps toadjust or control the volume of the commingled aqueous base fluid blend.

Testing may be repeated after each additive is combined with thecommingled aqueous base fluid blend until an optimal combination ofadditives is reached and the desired or predetermined physical andchemical characteristics are obtained. The testing and analysis may becarried out in real-time, thereby facilitating quick, on-the-fly andas-needed changes to the additive concentration or commingled aqueousbase fluid volume.

In yet another embodiment, samples of the commingled aqueous base fluidblend are collected and analyzed manually. The additives are manuallyintroduced or the volume of the commingled aqueous base fluid blend iscontrolled manually so that the commingled aqueous base fluid blendachieves the desired physical and chemical characteristics.

The commingled aqueous base fluid blend may be delivered to one or morefracturing fluid tanks or holding pits or tanks at the well site. Yetanother round of testing may be conducted on samples of the commingledaqueous base fluid blend at the well site to determine thecharacteristics of the commingled aqueous base fluid blend to bedelivered downhole. In one embodiment, testing at the well site iscarried out in real-time using field test kits. The concentration of theadditives and/or the volume of the commingled aqueous base fluid blendcan quickly be adjusted or changed depending on the composition, flowrate, physical and chemical properties required for fracturingoperation.

In another embodiment, the commingled aqueous base fluid blend is pumpedto a hopper or mixing equipment for proper mixing of any additionaladditives or proppants introduced to the aqueous base fluid blend at theproduction site to create the aqueous based fracturing fluid orfracturing fluid. Controlled volumes of fracturing fluid which comprisedesired concentration or dosage of the additives are then pumped to theformation at sufficient pressure and flow rates to fracture theformation. Since the volumes of fracturing fluid and the additive dosageis controlled on-demand, the fracturing operation is effective andcost-efficient.

Test Results

1. Blending of Spudder Water and Pond (or Fresh) Water.

Two water sources, a spudder water and pond water were used to formulatea slickwater fracturing fluid. The two water sources were initiallyanalyzed for key parameters, listed below in Table 1, required by thewell reservoir and the fracturing fluid formulation. The primaryconsideration in blending the fluids was to obtain a non-scaling andnon-corrosive aqueous base fluid as defined by the Langelier SaturationIndex (LSI). The Langelier Saturation index (LSI) is a well-knownequilibrium model which provides an indicator of the degree ofsaturation of water with respect to calcium carbonate. The LSI can beinterpreted as the pH change required to bring water to equilibrium. Ifthe LSI is negative, there is no potential for scaling and the waterwill dissolve calcium carbonate. However, a negative LSI value indicatespropensity for corrosion. If the LSI is positive, on the other hand,scales may form and calcium carbonate precipitation may occur. Ideally,in production operation, the LSI for the fracturing fluids should becloser to zero or in the negative (corrosive) range.

TABLE 1 Key Parameters Spudder water Pond water Blended water Sodium,ppm 783 3 378 Calcium, ppm 15 4 17 Magnesium, ppm 7 2 4 Barium, ppm <1<1 <1 Potassium, ppm 8 16 8 Iron, pp. 1 <1 <1 Total Alkalinity, 386 56220 ppm Carbonate 67 0 16 alkalinity, ppm Bicarbonate 320 56 204alkalinity, ppm Sulfate, ppm 16 <5 7 Chloride, ppm 1010 <20 540 pH 8.9 88.8 Specific gravity 1,002 1,000 1,002 Total Dissolved 2226 80 1175solids, ppm Total Hardness, 64 18 62 ppm Scaling Index, 1.00 −0.75 0.85LSI @ 50° C.

The initial data for the two water sources is listed above in Table 1.As shown in FIG. 1, calculation of the LSI value for the spudder wateris greater than zero, which indicates it to be scaling. It may beundesirable to have scaling tendencies in an aqueous base fluid used informulating a fracturing fluid because it interferes with the mainobjective of fracturing the formation. Conventional practice would betreat the spudder water with chemical additives at the well site toobtain a LSI value less than zero. In this test, the spudder water wasblended with the pond water to form a “blended water” with morefavorable LSI values even prior to any chemical treatments.Advantageously, the blending of the two water sources created an aqueousbase fluid that is more desirable and required less chemical treatment.

An optimum blend volume ratio of 48:52 spudder water to pond water wascreated based upon maximum volume usage of spudder pond water, shiftingof the LSI value towards a non-scaling, minimally corrosive fluid, andminimum additive treatment. The maximum volume usage of the spudderwater may be desirable as a means to recycle the water previously usedto spud the well and avoid future disposal cost. The blended water usingspudder water and pond water still had an unacceptable LSI value due tothe alkalinity concentration and pH. The chemical additive, TDP 452, aninorganic acid with corrosion inhibitor was recommended to treat theblended fluid to result in a final LSI of less than zero indicating anon-corrosive and non-scaling fluid. Based upon the chemical compositionof the blended waters as given in Table 1 and modeling using the LSIequation, an alkalinity value of less than 100 mg/l and pH of less than8.0 were set as the threshold value on the final treated fluid.

The real-time analysis, water transfer, additive injection point andcontrol mechanism is illustrated in FIG. 2. Conventional practice is totreat water onsite in the fracturing fluid tanks. Disadvantages of theconventional practice may include inadequate mixing of treatmentchemicals and potential for over or under treatment of chemicaladditives. This testing showed that after blending of the waters nearthe water source location, chemical treatment may be added inline as thefluid is transported towards the well site. The spudder water and pondwater are blended and treated simultaneously with TDP 452. As thetreated blended water is transported to the well site the injectedchemical additive. TDP 452 has time to mix homogeneously, it ismonitored and analyzed at various points including after initialintroduction of TDP 452, at the fracturing fluid tanks and just prior toformulation of the final slickwater fracturing fluid. At each of thepoints of analysis as shown in FIG. 2, two parameters, alkalinity and pHwere monitored. As the alkalinity and pH deviated from the thresholdvalue, the TDP 452 chemical injection pump was adjusted accordingly. Theinjection points for TDP 452 were placed immediately after blending ofthe two water sources, inline during water transport to the fracturingfluid tank storage and inline between water transport from thefracturing fluid tank storage to the well bore. These multiple chemicalinjection points and real time analyses ensured proper treatment andquality control.

This well was fractured in eight stages, utilizing a slick waterfracturing system. Table 2 list the volumes of each source of waterutilized for each fracturing stage. As shown in FIG. 3, the LSI value ofthe treated blended water during each fracturing stage was monitored inreal time and maintained to shown constant compliance to specifications.This was accomplished by continuous monitoring downstream of theadditive treatment injection points and feedback of data to additiveinjection points for appropriate adjustments.

TABLE 2 Total Volume Stage Spudder water Pond water Pumped 1 5060 bbl5,710 bbl 10,770 bbl 2 4,340 bbl 4,760 bbl 9100 bbl 3 3,900 bbl 4,550bbl 8450 bbl 4 6,450 bbl 7,680 bbl 14,130 bbl 5 4,380 bbl 5,410 bbl 9790bbl 6 4,100 bbl 4,320 bbl 8420 bbl 7 3,980 bbl 4,440 bbl 8420 bbl 83,640 bbl 4,130 bbl 7770 bbl2. Blending of Fluids from a Multiple Water Sources Followed by BiocideTreatment.

Multiple water sources, lake water, reserve pit (#1) water and waterfrom a second (#2) pit were used to formulate the fracturing fluid. Thewater sources were initially analyzed for key parameters, listed inTable 3 as required by the well reservoir and fracturing systemformulation. The primary considerations included non-scaling, minimallycorrosive water as defined by LSI along with ensuring that the blendedwater was bacteria free.

The initial analytical data on the three water sources is listed inTable 3. As shown in FIG. 4, the LSI value for the reserve pit and thesecond pit water are greater than zero, indicating scaling water.Conventional practice would be to treat each of these water sourcesindividually with chemical additives to shift the LSI to a value equalto or less than zero. In this test, these multiple sources of water wereblended, resulting in a more favorable LSI value.

TABLE 3 Blend A Blend B Lake Lake + Lake + water Reserve Reserve ReserveReserve Parameters Water pit # 1 pit #2 Pit #1 Pit #2 Calcium, ppm 2 5316 12 4 Magnesium, 2 19 4 5 2 ppm Iron, pp. 3 3 0.8 3 2.6 TotalAlkalinity, 18 192 111 53 37 ppm Hydroxide 0 0 0 0 0 Alkalinity, ppmCarbonate 0 0 9 0 0 alkalinity, ppm Bicarbonate 18 192 111 53 37alkalinity, ppm Sulfate, ppm <10 <10 <10 <10 <10 Chloride, ppm <28 15242889 327 598 pH 6.72 7.66 8.74 7.48 7.53 Total Dissolved 115 2896 1005671 293 solids, ppm Total Hardness, 10 210 55 60 19 ppm Bacteria, cfu/ml14500 102,000 Scaling Index, −2.86 0.44 0.52 −0.93 −1.38 LSI @ 50° C.

Two optimum blends utilizing a combination or each pit water source withthe lake water was created based upon maximum volume usage of reservepit #1 and reserve pit #2 waters with minimum additive treatment. Themaximum volume usage of these two reserve pit waters is highly desirableas a means to recycle the previously used water and avoid futuredisposal cost. In this particular case, the primary problems werescaling, corrosivity and bacterial contamination of reserve pit watersas illustrated in the LSI graph in FIG. 4 and bacterial contaminationdata listed in Table 1. The initial analytical data was used to dictatethe blending of one part reserve pit #1 water with four parts lake waterto result in non-corrosive and non-scaling water as shown in FIG. 4. Anadditive, namely, a bromine-based biocide, such as, BioRid®. (BioRid isa registered trademark of TETRA Technologies, Inc. of Houston, Tex.),was recommended for addition to the blended water to address thebacterial contamination. Additional volumes of water was made up withone part of pit Water #2 to four parts of lake water to result innon-corrosive and non-scaling water as shown in FIG. 4. A recommendationof treatment of biocide to the blended water was also made to addressthe bacterial contamination. The blending of the reserve pit waters withthe lake water eliminated the use chemical additives to achieve asubstantially less non-corrosive and non-scaling water.

Both blended waters required treatment with a biocide to perform acomplete kill of bacteria. Biocide treatments are especially sensitiveto contact time for effective bacterial kill. Conventional practice isto treat water with additives such as biocides at the rig site in thefracturing fluid tanks. The disadvantages of the conventional practiceinclude inadequate missing of the treatment chemicals, insufficient killtime for biocide to perform a complete bacterial kill and potential overor under treatment of chemical additives. These testing shows that afterblending of the waters near the location of the water source, chemicaltreatment with a biocide may be performed inline as the fluid istransferred towards the well site. As the treated water is transportedto the well site, the injected chemical additive has time to mixhomogeneously and perform a complete bacterial kill.

The real-time analysis, additive injection point and control mechanismfor bacterial treatment with the biocide on blended water is illustratedin FIG. 5. In this particular application of the biocide, real-timeanalysis monitored the residual bromine concentration in the water toindirectly assure bacterial kill. The threshold value for maintaining acontinuous effective bacterial kill was 10 ppm residual bromine.Continuous real time sampling and analyses occurred after blending ofthe Waters, at the fracturing fluid tanks and after water is used toformulate the final fracturing fluid. At all these points, the real-timeanalysis data was utilized continuously to monitor residual bromine andadjustments of the treatment rate of the biocide were made at theinitial blending of waters and prior to injection of fracturing fluidinto the well bore. The placement of injection points for the biocidewas designed to ensure a complete kill of bacteria and quality assuranceof required residual active biocide for effective downhole control ofbacteria.

This well was fractured in thirteen stages, utilizing a slick waterfracturing fluid. Table 4 list the volumes of each source of waterutilized for each fracturing stage. As shown in FIG. 6, effectivebiocidal treatment was maintained during all stages as all sample pointbromine residuals were above 10 ppm. The treated blended water duringeach fracturing stage was monitored in real time and maintained to shownconstant compliance to specifications. This was accomplished bycontinuous monitoring downstream of the additive treatment injectionpoints and feedback of data to additive injection points for appropriateadjustments.

TABLE 4 Total Volume Stage # Reserve Pit Water Lake Water Pumped 1 3,300bbl 13,200 bbl 16,500 bbl 2 3,200 bbl 12,800 bbl 16,000 bbl 3 3,300 bbl13,200 bbl 16,500 bbl 4 3,200 bbl 12,800 bbl 16,000 bbl 5 3,100 bbl12,400 bbl 15,500 bbl 6 3,100 bbl 12,400 bbl 15,500 bbl 7 3,100 bbl12,400 bbl 15,500 bbl 9 3,000 bbl 12,000 bbl 15,000 bbl 10 3,100 bbl12,400 bbl 15,500 bbl 11 2,940 bbl 11,760 bbl 14,700 bbl 12 3,000 bbl12,000 bbl 15,000 bbl 13 3,000 bbl 12,000 bbl 15,000 bbl 14 3,100 bbl12,400 bbl 15,500 bbl

In another embodiment, one or more proppants and/or other substancescomprising friction reducers, that improve the flow characteristics andeffectiveness of the fracturing fluid in fracturing the rock formationare also pumped into the hopper along with the commingled aqueous basefluid blend. Proppants comprise sand, fine gravel or glass heads thatserve to keep the fracture open after the fracturing operation. Fluidloss agents may be added to the hopper. Fluid loss agents partially sealoff the more porous sections of the formation so that the fracturingoccurs in the less porous strata. Viscosifying agents may also be addedto the hopper. Viscosifying agents allow the propping agent to bedispersed within the fluid during injection so that it is more easilycarried to the pay zone. The adjusted aqueous base fluid blend,proppants and other substances are blended in the hopper to form aslurry. In one embodiment of this invention, samples of the slurry aretested by the well operators and adjustments are made to one or morecomponents of the slurry.

Powerful fracturing pumps inject the fracturing fluid to the formationthrough the well bore. The fracturing fluid is pumped in sufficientvolumes, and at sufficient pressure and flow rates to fracture theformation. The fracturing fluid is pumped in via the casing or tubing orthrough the annular space. Electronic monitoring systems provideconstant feedback to the well operators. Fluid flow rates and pressurebuildup within the formation are monitored to ensure that fracturinggrowth rate is safe and controlled. The fracturing is generated andpropagated as pumping continues to permit placement of the proppants.The pressure is then relieved allowing the oil to seep through thefractures in to the well bore where it is pumped hack to the well bore.The fractured formation is held open after the pressure is released byone or more proppants in the slurry. The well is then shut in andbackflowed to remove the fracturing fluid from the propped fracture. Thefracturing fluid is recovered as flowback water.

The flowback water is sampled to determine its physical and chemicalproperties and to determine residual trace quantities of biocides and/orother contaminants. In one embodiment, the flowback water is pumped hackto a storage tank for use as aqueous base fluid in the same or otherfracturing operation.

In another embodiment, a method for the controlled delivery of afracturing fluid to a well bore to control scaling and corrosion withinthe well bore comprises predetermining the physical and chemicalproperties of an optimal aqueous base fracturing fluid. One or moresamples of a commingled aqueous base fluid may be tested prior to pipingto the well bore to analyze its physical and chemical properties. One ormore additives are introduced into the commingled aqueous base fluidprior to delivering it to the well bore. The selected additives comprisesubstances that reduce scaling and corrosion within the well bore. Oneor more samples of the commingled aqueous base fluid are tested afterthe additives have been introduced, but prior to delivery to well bore,to analyze their physical and chemical properties. The analyzed resultsare evaluated to ascertain if they are in line with the predeterminedphysical and chemical properties. The physical and chemical propertiesdata resulting from the testing and analyzing may be sent to a controlcenter. The necessary adjustments to the physical and chemicalproperties of the commingled aqueous base fluid can be made until thefracturing fluid is or is substantially less non-corrosive andnon-scaling.

In another embodiment, the commingled aqueous base fluid is pumped ortrucked to a set of fracturing fluid tanks. The fracturing fluid tanksmay be located either onsite or offsite from the well location. One ormore additives are introduced to the commingled aqueous base fluidthrough one or more metering pumps. The additives are mixed inline andblended with the commingled aqueous base fluid. One or more samples ofthe commingled aqueous base fluid blend are collected from samplingports and tested at a control center. The result is processed andanalyzed by one or more computers located at the control center. Thecomputers transmit instructions for making necessary adjustments to theone or more metering pumps to adjust or control the amount of additiveto be introduced to the commingled aqueous base fluid. The commingledaqueous base fluid blend is then delivered to the production facilityfor fracturing the formation.

A method for delivering a controlled volume of fracturing fluid to thewellbore is disclosed in another aspect of the invention. Currentpractice involves pumping large volumes of fracturing fluid varying froma few hundred gallons to over hundreds of thousand gallons per well.Some of the fracturing fluid is immediately recovered as flowback waterto maintain the productivity of the wells and reduce plugging of thefractured formations due to fracturing fluid residues and filter cakebuildup thereon. Due to increasing emphasis by regulatory bodies onminimizing environmental impact, disposal of fracturing fluids has alsobecome a problem, especially if the fluids contain environmentallyoffensive additives and biocides. The various embodiments of theinvention teach the introduction of controlled volumes of fracturingfluids into the formation. The method of the invention teachescollection of and analysis of the commingled aqueous base fluid samples,obtained by commingling aqueous base fluids from one or more sources, atone or more locations offsite from the production zone. Controlleddosage of additives is introduced to the commingled aqueous base fluiduntil the commingled aqueous base fluid achieves the predeterminedphysical and chemical properties. Since the commingled aqueous basefluid is blended well with the additives, and since the composition andphysical and chemical properties of the commingled aqueous base fluidblend are predetermined and adjusted depending on the requirements ofthe fracturing operation, the method of this invention can deliverreduced or controlled volumes of the fluid to the production site andthen to the formation for the fracturing operation. The volume of thefracturing fluid can also be adjusted “on the fly” depending on thefracturing operation, since the composition and physical and chemicalproperties of the commingled aqueous base fluid are pre-tested and,therefore, known before it is even delivered to the production site.

The methods of the invention further comprises the introduction of oneor more additives in a fracturing operation by using the commingledaqueous base fluid as a carrier or a delivery conduit. Additives performseveral beneficial functions such as pH modification, killing microbialagents and corrosion inhibition. In one aspect, one or more additivesare introduced into the commingled aqueous base fluid using one or moremetering pumps. The concentration of the additives in the commingledaqueous base fluids is adjusted by a multi phase process of testing andanalysis, both offsite and at the production facility.

In another embodiment, a method for the controlled introduction of oneor more environmentally friendly biocides in a fracturing operation isdisclosed. In prior fracturing operations, the biocides that were usedwere often toxic. Moreover, since the biocides were added to thefracturing fluid at the production site, the biocides were nothomogeneously dispersed in the fracturing fluid and therefore, largerconcentrations of the biocides were introduced in the fracturing fluidto achieve the desired “kill rate” for bacilli and other livingorganisms. At the conclusion of the fracturing operation, the fracturingfluid containing the toxic biocides was labeled waste water anddisposed. In one embodiment of the present invention, one or moreoxidizing and organic bromine-based biocides are introduced to theaqueous base fluids using metering pumps. On the contrary, thebromine-based biocides of the invention can be measured before theirintroduction in the commingled aqueous base fluid and then sampled andtested after they are added to the commingled aqueous base fluid. Thedosage of the bromine biocides is controlled and adjusted to achieve thedesired concentration. The contact time for the bromine biocide isdesigned into the hold time in the fracturing fluid tanks.Advantageously, since the bromine biocides are oxidizable andbiodegradable, they are less toxic to the environment. If the brominebiocide is spilled or leaked, it is gone in minutes to hours due to thereactivity of the biocide with light and elements in the environment.This also negates the necessity, and associated expenses, to dispose thebromine biocides. Advantageously, the bromine based biocides of theinvention also have a faster microbial kill rate and a level ofstability which when applied to the commingled aqueous base fluidresults in purer commingled aqueous base fluid. Pure fluids arepreferred in fracturing operations. In one embodiment of the invention,the flowback fluid is collected and tested to determine the presence ofany residual biocides. The flowback fluid may be then treated withadditives to neutralize the residual biocide prior to disposal and/ortransfer to a holding tank.

The method of this invention teaches the stimulation of oil and gaswells by controlling the concentration of additives and fracturing fluidvolumes needed in a fracturing operation The method of controllingadditive concentration and fracturing fluid volume as taught by thisinvention can increase the production rate of the well by forming highlyconductive holes in the fractured formation and improve the economics ofthe fracturing operation. Advantageously, the method of the inventionreduces the costs involved in fracturing fluid clean-up and disposal ofrecovered fracturing fluids. Furthermore, in one aspect, the method ofthe invention provides an environmentally friendly method to stimulatethe oil and gas bearing formation by controlled introduction ofnon-toxic and biodegradable additives.

While the invention has been particularly shown, described andillustrated in detail with reference to one or more embodiments andmodifications thereof, it should be understood by those skilled in theart that equivalent changes in form and detail may be made thereinwithout departing from the true spirit and scope of the invention asclaimed.

The invention claimed is:
 1. A method for controlled delivery of afracturing fluid to a well bore comprising: (a) identifying a pluralityof sources of an aqueous fluid for the fracturing fluid and providingpredetermined characteristic data for the fracturing fluid; (b) testingthe identified plurality of sources of aqueous fluid to determine eachsource's characteristics; (c) comparing the tested physical and chemicalcharacteristic data of each source of aqueous fluid identified in step“a” to the predetermined characteristic data for the fracturing fluid toidentify suitability of each identified source for fracturingoperations; (d) after step “c”, if a favorable comparison is made to thepredetermined physical and chemical characteristic data for thefracturing fluid, transporting aqueous fluid, obtained from theirrespective source identified in step “a” to a well site for fracturingoperations at least one of the sources that compared favorably in step“c” to the predetermined characteristic data for the fracturing fluid;(e) during step “d” testing the aqueous fluid being transported, andcomparing the characteristic data to the predetermined characteristicdata for the fracturing fluid; (f) during steps “d” and “e”, in theevent of a failed comparison, introducing at least one additive to treatthe aqueous fluid being transported; (g) repeating steps “e” and “f”until the aqueous base fluid being transported achieves at least onepredetermined characteristic in the predetermined characteristic data;and (h) after step “g”, transporting the treated aqueous fluid to afracturing system, the fracturing system including a fracturing pump;and (i) after step “h”, formulating the fracturing fluid with thetreated aqueous fluid, and the pump of the fracturing system pumping thefracturing fluid into the wellbore for fracturing operations.
 2. Themethod of claim 1, wherein testing in step “e” is performed downstreamof the at least one additive introduced in step “f” and upstream of thefracturing system.
 3. The method of claim 2, wherein the at least oneadditive includes a bromine biocide, and further comprising the step oftesting at least one sample of flowback fluids at the conclusion of thefracturing operations to identify residual traces of the brominebiocide.
 4. The method of claim 1, wherein during step “h” the aqueousfluid is delivered to the fracturing system located proximate to thewell site.
 5. The method of claim 1, wherein first during step “d” theaqueous fluid is first delivered to a first set of fracturing fluidtanks located proximate to the source of aqueous base fluid, and secondduring step “h” delivered to the fracturing system located proximate tothe well site.
 6. A method for controlled delivery of a fracturing fluidto a well bore comprising: (a) identifying a plurality of sources of anaqueous fluid for the fracturing fluid and providing predeterminedcharacteristic data for the fracturing fluid; (b) testing the identifiedplurality of sources of aqueous fluid to determine each source'scharacteristics; (c) comparing the tested physical and chemicalcharacteristic data of each source of aqueous fluid identified in step“a” to the predetermined characteristic data for the fracturing fluid toidentify suitability of each identified source for fracturingoperations; (d) after step “c”, if a favorable comparison is made to thepredetermined characteristic data for the fracturing fluid, for aplurality of the sources that compared favorably in step “c” to thepredetermined characteristic data for the fracturing fluid, comminglingaqueous fluid from the plurality of sources of aqueous fluid, andtransporting the commingled aqueous fluid to a well site for fracturingoperations; (e) during step “d” testing the commingled aqueous fluidbeing transported, and comparing the characteristic data to thepredetermined characteristic data for the fracturing fluid; (f) duringsteps “d” and “e”, in the event of a failed comparison, introducing atleast one additive to treat the commingled aqueous fluid beingtransported; (g) repeating steps “e” and “f” until the commingledaqueous fluid being transported achieves at least one predeterminedcharacteristic in the predetermined characteristic data; and (h) afterstep “g”, transporting the treated commingled aqueous fluid to afracturing system, the fracturing system including a fracturing pump;and (i) after step “h”, formulating the fracturing fluid with thetreated commingled aqueous fluid, and the pump of the fracturing systempumping the fracturing fluid into the wellbore for fracturingoperations.
 7. The method of claim 6, wherein the plurality ofidentified sources of aqueous fluid are include different types ofsources of aqueous base fluid.
 8. The method of claim 7, wherein theplurality of identified sources of aqueous fluid fall within to one twoor more of the following types of fresh water sources: lakes, rivers,ponds, creeks, streams and well water.
 9. The method of claim 6, whereintesting in step “e” is performed downstream of the at least one additiveintroduced in step “f” and upstream of the fracturing system.
 10. Themethod of claim 9, wherein the at least one additive includes a brominebiocide, and further comprising the step of testing at least one sampleof flowback fluids at the conclusion of the fracturing operations toidentify residual traces of the bromine biocide.
 11. The method of claim6, wherein during step “h” the commingled aqueous fluid is delivered tothe fracturing system located proximate to the well site.
 12. The methodof claim 6, wherein first during step “f” the commingled aqueous fluidis delivered to a first set of fracturing fluid tanks located proximateto the source of aqueous fluid, and second during step “h” delivered tothe fracturing system located proximate to the well site.
 13. The methodof claim 6, wherein during step “f” a plurality of different additivesare introduced and testing of the commingled aqueous fluid beingtransported is made of each of the plurality of different additivesintroduced.